Agronomy Fact Sheet Series Fact Sheet 29
Soil Texture
Soil texture is an important soil characteristic in the light-textured sandy soils. The cation that drives crop production and field exchange capacity of the soil increases with management. The textural class of a soil is percent clay and organic matter (Agronomy determined by the percentage of sand, silt, Fact Sheet #22) and the pH buffering capacity and clay. Soils can be classified as one of four of a soil (its ability to resist pH change upon major textural classes: (1) sands; (2) silts; (3) lime addition), is also largely based on clay loams; and (4) clays. In this fact sheet, we will and organic matter content (Agronomy Fact discuss the importance of soil texture, different Sheet #6). Soil tilth (how easily or difficult a methods to determine soil texture, and the field is tilled) is influenced by texture, soil impact of texture on management decisions. moisture, aeration, and organic matter as well.
Importance of Soil Texture Soil Textural Classes A clay soil is referred to as a fine-textured soil The combined portions of sand, silt, and clay in whereas a sandy soil is a coarse textured soil. a soil determine its textural classification. Sand Numerous soil properties are influenced by particles range in size from 0.05–2.0 mm, silt texture including: ranges from 0.002–0.05 mm, and the clay fraction is made up of particles less than 0.002 Drainage mm in diameter. Gravel or rocks greater than Water holding capacity 2 mm in diameter are not considered when Aeration determining texture. Once the sand, silt, and Susceptibility to erosion clay percentages of a soil are known, the Organic matter content textural class can be read from the textural Cation exchange capacity (CEC) triangle (Figure 1). For example, a soil with pH buffering capacity 40% sand, 40% silt and 20% clay would be Soil tilth classified as a loam. Soil texture determines the rate at which water drains through a saturated soil; water moves more freely through sandy soils than it does through clayey soils. Once field capacity is reached, soil texture also influences how much water is available to the plant; clay soils have a greater water holding capacity than sandy soils. In addition, well drained soils typically have good soil aeration meaning that the soil contains air that is similar to atmospheric air, which is conducive to healthy root growth, and thus a healthy crop. Soils also differ in their susceptibility to erosion (erodibility) based on texture; a soil with a high percentage of silt and clay particles has a greater erodibility than a sandy soil under the same conditions. Differences in soil texture also impacts organic matter levels; organic matter breaks down faster in sandy soils than in fine-textured soils, given similar environmental conditions, tillage Figure 1: A soil textural triangle is used to determine soil and fertility management, because of a higher textural class from the percentages of sand, silt, and clay amount of oxygen available for decomposition in the soil.
Department of Crop and Soil Sciences 1 College of Agriculture and Life Sciences Texture should not be confused with structure, (NRCS) website (http://websoilsurvey.nrcs. which refers to how soil particles are usda.gov/app/WebSoilSurvey.aspx; once the aggregated together. It is possible to improve area of interest is defined, surface texture soil structure via best management practices information for each soil map unit can be such as reduced tillage. However, it is very generated by navigating to Soil Data impractical (expensive) and thus ill-advised to Explorer/Soil Properties and Qualities/Soil modify a soil’s texture. Physical Properties/Surface Texture).
How to Determine Soil Texture Soil Management Groups New York soils are divided into five different In the laboratory mineral soil management groups (I through V) The most accurate way involves submitting a based on soil texture and parent material from sample to a soil testing laboratory for which the soil was formed. Group I soils are determination of the percentage of sand, silt, medium- to fine-textured. Group II soils are and clay by using either the pipette method moderately fine- to medium-textured. Group (most accurate) or the hydrometer method III soils range from medium-textured to (less accurate but quicker). The Cornell moderately-coarse soils. Group IV has coarse- Nutrient Analysis Laboratory (CNAL) uses the to medium-textured soils. Group V contains pipette method. For more information contact: coarse- to very coarse-textured soils. Knowing Cornell Nutrient Analysis Laboratory the soil type of a specific field allows for more Phone: (607) 255-4540; accurate fertility management. For example, Email: [email protected] the coarse-textured soils in group V are more Website: www.css.cornell.edu/soiltest susceptible to potassium deficiency than clay soils in group I. In addition, group I soil are In the field generally more susceptible to runoff Soil texture can be estimated in the field by (moderately to poorly drained soils) and more observing its physical characteristics. likely to need tile drainage for early planting, optimum plant growth, and timely harvests A sandy soil feels gritty and falls apart easily (see also Agronomy Fact Sheet #19). if formed into a ball when moist. A loamy soil feels somewhat gritty, yet is Additional Resources: easy to work; it has relatively even amounts o Cornell University Agronomy Fact Sheet #6 (Lime of sand, silt, and clay; if formed into a ball Recommendations), #19 (Soil Management Groups), when moist, it holds its shape, yet still and #22 (Cation Exchange Capacity) breaks apart easily when squeezed. http://nmsp.css.cornell.edu/publications/factsheets.asp A silty soil breaks apart easily and has a floury appearance when dry. When moist, Disclaimer: silty soils have a slick feel and form no This fact sheet reflects the current (and past) authors’ best effort to interpret a complex body of scientific research, ribbon when pinched between fingers and and to translate this into practical management options. thumb. Following the guidance provided in this fact sheet does not A clayey soil forms large, hard clods and assure compliance with any applicable law, rule, regulation cracks form on the surface. Clayey soils feel or standard, or the achievement of particular discharge levels from agricultural land. sticky and are bendable when moist. A ribbon can be formed when moist by For more information pinching soil between fingers and thumb. A longer ribbon formed before it breaks indicates a higher amount of clay.
From a soil map If the field location is known, a soil survey map Nutrient Management Spear Program can be used to determine the textural class of http://nmsp.css.cornell.edu the soil. Maps are available through local
Cornell Cooperative Extension (CCE) or Soil Wayne Berry, Quirine Ketterings, Steve Antes, Steve Page, and Water Conservation District (SWCD) Jonathan Russell-Anelli, Renuka Rao and Steve DeGloria offices, or, for many New York counties, via 2007 the National Resources Conservation Service
Department of Crop and Soil Sciences 2 College of Agriculture and Life Sciences